1. Field of the Invention
This invention relates to materials, devices, and methods for corrosion protection.
2. General Background
Reinforcing steel members are used in a number of applications, including “rebar” in concrete. But the steel tends to corrode when it comes into contact with chlorides, such as from deicing salts or sea water.
To protect the reinforcing steel against corrosion, it may be covered with fusion-bonded epoxy coatings. Fusion-bonded epoxy coatings are applied as a powder under controlled temperature conditions at a coating facility. The powder is typically electrostatically applied to reinforcement that has been cleaned and grit-blasted to remove surface contaminants and to provide a uniform blast anchor profile. After grit-blasting, reinforcing bars are heated to approximately 232° C. (450° F.) and the powder is applied. The powder fuses to the heated bar surface and cures as the reinforcing bars cool to room temperature. A combination of water and air cooling may be used to control the rate of epoxy curing. As an alternative to electrostatic spraying of epoxy powder material, reinforcing steel may be dipped into a fluidized bed of epoxy/powder after the bar is heated.
These coatings work well to protect most of the reinforcing element, but they are often ineffective in protecting the splice or joint between two adjoined pieces of reinforcing steel. These splices or joints can be created by a mechanical coupler or by welding. In either case, corrosion protection is required. Mechanical coupler splices are typically applied bare, without fusion-bonded epoxy coatings. Similarly, the bare metal of a weld splice needs protection. Also, the heat from welding can damage the epoxy coating on adjacent portions of the rebar.
Epoxy, paint, or other coatings can be hand-applied to the spliced region, but this process is problematic, since such coatings can be difficult to apply by hand, and since they require additional surface preparation. Also, hand-applied coatings often fail to provide adequate protection. In addition, field applied paints and epoxies require cure time prior to handling and have limited application windows that depend on the environmental conditions such as humidity and temperature.
To overcome the problems of hand-coating, heat shrinkable corrosion protection sleeves have been developed, such as those revealed in U.S. Pat. Nos. 6,265,065 and 3,610,291. However, these sleeves suffer from a number of disadvantages. First, because there is no way to tension the sleeves, there may be gaps at the end, even after the sleeves have been heated. Second, because they are pre-cut before application, problems can arise if the sleeves are cut to the wrong length for a particular splice region. For instance, if a sleeve is cut too short, there is no way to add “more” of the sleeve to protect the uncovered area. Third, because every sleeve has a relatively fixed diameter, these sleeves cannot easily be adapted to splice regions of varying diameter. Thus, for any given job site, workers might need to bring a plurality of sleeves of varying diameters. Fourth, the sleeves are prone to contamination, since they are typically installed in batches, and then heated in batches. During the time between installation and heating (which may be substantial), the sleeves are just hanging in the spliced region, and contaminants may fall in. Therefore, there is a need for a material or product that can conveniently and effectively protect spliced regions from corrosion, without the disadvantages of the prior art.